<svg width="500px" height="610px" xmlns="http://www.w3.org/2000/svg">
<defs>
    <filter id="filter" filterUnits="objectBoundingBox">
        <feFlood/>
        <feDiffuseLighting lighting-color="rgb(0, 255, 0)" x="-120" y="85">
            <fePointLight x="250" y="200" z="50"/>
        </feDiffuseLighting>
        <feComponentTransfer>
            <feFuncG type="discrete" tableValues="0 1"/>
        </feComponentTransfer>
    </filter>
</defs>
<rect x="110" y="150" width="400" height="320" fill="none" filter="url(#filter)"/>
<!-- Mask off slight differences in point light radius -->
<circle cx="250" cy="200" r="85" fill="none" stroke="gray" stroke-width="20"/>
</svg>